94 DEPARTMENT OF THE NAVAL SERVICE 



6 GEORGE V, A. 1916 



In addition to the data already referred to, evidence was obtained to show that 

 either the females are much more numerous than the males or the individuals of one 

 sex associate in separate shoals. Among the forty-eight fish examined on July 16 

 (Nos. 53 to 100) there were only two males ; among the one hundred and twenty-eight 

 examined on July 22 there were forty-six males ; among the one hundred and twenty- 

 four examined on July 30 there were thirty-five males; among the four hundred and 

 twenty-eight examined on July 31 there were one hundred and thirty-one males. 

 From these figures it would appear that the second explanation suggested, namely, 

 that the females are much more numerous than the males, is the probable one. 



SUMMARY. 



Thus in the investigation of the life-history of the hake, 780 individuals were 

 examined. From the data obtained, length-frequency curves were drawn which 

 showed that the average length of the females examined was greater than that of the 

 malei.. An examination of the scales indicated that these males and females were the 

 same age. Thus it appeared that the shoals are composed almost entirely of fish of 

 one age and that the females are longer than the males of the same age. It is unfor- 

 tunate that practically all the fish examined were in their fourth year. These fish 

 were representative of all those caught in the St. Andrews district during the season, 

 the size of all the hake brought in being remarkably uniform. Length-frequency 

 ^'urves for the individuals of either sex in their fourth year were drawn, and these 

 were compared with length-frequency curves for the sexes at the end of each year of 

 their growth, constructed from the lengths calculated from scale diagrams, upon the 

 assumption that the growth of the scales is proportional to that of the fish. In pre- 

 paration for the determination of age, and the construction of scale diagrams, the 

 morphology of the scales was carefully examined. It should be mentioned that the 

 vertebrae of a considerable number of individuals were cleaned and examined as a 

 basis of age determination, to be a check upon the scales. It was found, however, 

 that the rings of growth were too indefinite to be of much service, and this method 

 was soon abandoned. 



Finally, from the means of the length-frequency curves based upon the scale 

 diagrams, rate of growth curves for the two sexes were constructed. These showed 

 in the first place, that the rate of growth was fairly uniform during the first three 

 years, indicating that spawning does not take place before the fourth year; in the 

 second place, that the rate of growth decreases in each succeeding year for the first 

 three years; in the third place, that the excess in rate of growth of the females over 

 the males increases in each succeeding year during the same period. 



In concluding this report I wish to express my appreciation of the direction and 

 assistance of Dr. J. "W. Mavor in the accumulation and working up of the data, and 

 also of the assistance afforded in the former part of the work by all the members of 

 the staff at the. St. Andrews Biological Station in 1914. 



